The drive arrangements of motor vehicles typically comprise a motor and a transmission, by which the motor torque is transmitted to the drive wheels. Additionally, it is typical to provide brake control devices for special braking functions. Such braking functions are known, for example, by the names or terms: antislip regulation (ASR), electronic differential locking (EDS), and electronic stability program (ESP). The special braking functions are active when one or more of the wheels of the motor vehicle comprise a slip that exceeds a certain or determined value.
In a motor vehicle with a stepless automatic transmission, the transmission ratio of the automatic transmission is variable in a stepless manner and thus makes it possible to achieve the optimum utilization of the motor torque. For this purpose, the transmission ratio is regulated with a transmission controller or regulator, whereby the regulation can be carried out according to certain predefined strategies. If an increased slip now arises on one of the drive wheels, then this can lead to an increase of the regulation deviation in the transmission controller. The transmission controller would attempt to regulate-out this regulation deviation, which would lead to rapid changes of the transmission ratio and therewith to rapid changes of the moments or torques of the drive wheels. Rapid changes of the moments or torques of the drive wheels would, however, impair the effectiveness of the braking functions and lead to a repeated activation and deactivation of the braking functions. In order to avoid this disadvantage, a change or variation of the transmission ratio of the automatic transmission is prevented, as long as one of the braking functions is active.
This has as a result, that the motor torque will be sharply reduced by the antislip regulation for a long continuing period, but the motor rotational speed will continue to remain at a high level, during a longer drive on a driving path or roadway with a low coefficient of friction, for example a roadway covered with snow or ice, especially for a drive with a high driving or accelerator pedal angle, i.e. with a high acceleration desire of the driver. This leads to a bothersome high motor noise.